CN111596676B - Underwater Bessel light vision guiding method - Google Patents
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Abstract
An underwater Bessel light vision guiding method comprises the following steps: selecting a Bessel lens according to a target template of the marker lamp; the Gaussian beam in the Bessel marker lamp is presented as a line segment beam after passing through the Bessel lens; after the Bessel marker lamps are lightened, the light beam of each Bessel marker lamp forms a line segment, and the multiple light beam line segments form a marker lamp modal diagram; in the autonomous recovery process of the underwater unmanned vehicle, an image processing module in an underwater camera performs image processing on an obtained underwater Bessel marker lamp modal graph to extract line segment light beams and obtain coordinates of feature points under camera coordinates; acquiring coordinates and posture information of a camera coordinate system under a docking station coordinate system; and giving three-dimensional space coordinates and attitude information of the underwater unmanned vehicle under the docking station coordinate system. The invention has good adaptability and strong flexibility, can realize the miniaturization of the mechanical structure of the marker light, realizes the accurate extraction of the characteristic line segment of the marker light beam and improves the positioning precision.
Description
Technical Field
The invention relates to the technical field of underwater optics, in particular to an underwater Bessel optical vision guidance method.
Background
An Autonomous Underwater Vehicle (AUV) is an Underwater robot which executes Underwater operation tasks by using various sensors and other task modules, and performs Autonomous navigation, Autonomous decision and Autonomous control through energy equipment, navigation equipment and an execution mechanism carried by the AUV, and is widely applied to the fields of marine scientific research, marine engineering operation and national defense and military. However, the time of the AUV operating underwater is limited to the energy carried by the AUV to a great extent, and after the AUV completes a certain task, the AUV usually needs to be recovered to a water surface support platform so as to supplement the energy, recover data and download a new mission task. When working on large depths of the sea, the deployment and recovery of the AUV takes a relatively long time, and if the sea state of the working sea is poor, the recovery process increases certain risks. In order to improve the underwater operation time and work efficiency of the AUV and reduce the risk, the AUV is generally recovered autonomously by using an underwater optical vision technology.
Fig. 1 shows a conventional underwater multi-light-source light vision guiding method, an underwater camera 2 is assembled at the bow of an autonomous underwater unmanned vehicle AUV1, a docking station recovery device 3 is provided with a bell mouth-shaped (funnel-shaped) recovery cover, a marker light 4 with a large divergence angle is installed on the recovery cover, when the aperture of the recovery cover is small, the light spots of the marker light can be overlapped, so that the centroid of each light spot of a conventional marker light 6 is difficult to accurately extract from the image output by the underwater camera 2, and the AUV cannot be effectively positioned.
The light vision guidance is mainly used for capturing images of the marker lights of the docking station by using an AUV (autonomous underwater vehicle) bow camera and calculating the relative position by matching image characteristics with known characteristics for high-precision positioning. The existing optical vision guidance technology mainly comprises monocular vision guidance and binocular vision guidance.
In the existing guidance technology, whether monocular vision guidance or binocular vision guidance, the light source marker lamp at the docking station has the same problem:
(1) the centroid of the marker light is difficult to extract: in the optical visual guidance, high-precision pose resolving needs accurate extraction of the center position of a marker lamp, an LED lamp with a large divergence angle is generally adopted as an ideal circular marker lamp in the traditional optical guidance process, a marker lamp spot centroid in an image captured by a camera is extracted as a characteristic point of the marker lamp spot centroid, but the marker lamp is difficult to form an ideal circular spot under the influence of water and environmental noise, so that the centroid extraction of the marker lamp is inaccurate, and the positioning precision is influenced;
(2) the number of the marker lights is limited by the mechanical size, so that the miniaturization of the docking station device is limited: the LED marker light with large divergence angle can only extract the coordinate position of the light through the centroid of the light spot, at least 4 marker lights are needed to be discretely distributed on a docking station with the diameter of 1 m-3 m, the optical visual positioning is realized by utilizing the relative position information among the lights, if the diameter of the docking station is reduced, the light spots of a plurality of marker lights are difficult to separate and easy to overlap, and the marker lights cannot be effectively extracted, thereby seriously limiting the application of the technology in AUV autonomous recovery.
Disclosure of Invention
In view of the above, the present invention provides an underwater bessel light vision guiding method, so as to partially solve at least one of the above technical problems.
In order to achieve the above object, as an aspect of the present invention, there is provided an underwater bessel light vision guiding method, including the steps of:
selecting a Bessel lens according to a target template of the marker lamp;
the Gaussian beam in the Bessel marker lamp is presented as a line segment beam after passing through the Bessel lens;
after the Bessel marker lamps are lightened, the light beam of each Bessel marker lamp forms a line segment, and the multiple light beam line segments form a marker lamp modal diagram;
in the autonomous recovery process of the underwater unmanned vehicle, an image processing module in an underwater camera performs image processing on an obtained underwater Bessel marker lamp modal graph to extract line segment light beams and obtain coordinates of feature points under camera coordinates;
an image processing module in the underwater camera obtains coordinates and posture information of a camera coordinate system under a docking station coordinate system by utilizing the corresponding relation between the coordinates of the underwater Bessel marker lamp under the docking station coordinate system and the coordinates of the camera coordinate system;
an image processing module in the underwater camera provides three-dimensional space coordinates and attitude information of the underwater unmanned vehicle under a docking station coordinate system by utilizing the known conversion relation between a camera coordinate system and the underwater unmanned vehicle coordinate system.
And adjusting the bottom angle of the conical surface of the Bessel lens can realize the length adjustment of the line segment light beam.
The line-segment light beam is formed by utilizing a Bessel lens, keeps light intensity distribution unchanged within a certain distance from a self-luminous position, has high-intensity localized distribution, is formally represented as a light beam line segment with limited length, and the length of the light beam line segment can be changed by adjusting the Bessel lens.
The marker light target template is a specific target pattern formed by utilizing line segment light beams according to the self requirements of users, and the length of the line segment light beam in the template is known.
Based on the technical scheme, compared with the prior art, the underwater Bessel optical visual guidance method has at least one of the following beneficial effects:
1. the marker lamp adopts the diffraction-free line segment light beam generated by the Bessel lens as the marker lamp, and compared with the traditional large divergence angle LED marker lamp centroid extraction, the accuracy of line segment extraction of the line segment light beam is higher, so that the marker lamp extraction accuracy can be improved.
2. The traditional large-divergence-angle LED marker lamp can only extract the centroid to obtain the position information of the lamp, at least 4 lamp marker lamps are required to be used as guide lamps, and the Bezier marker lamp provided by the invention has the position information and also has the length and direction information, so that the Bezier marker lamp can provide more information, and the light vision positioning can be realized by utilizing 2 Bezier lamps, so that the number of the marker lamps is reduced, the arrangement of a recovery device on a small-size docking station is facilitated, and the size of the recovery device is reduced.
Drawings
FIG. 1 is a conventional underwater multi-source light vision guidance method;
FIG. 2 is a diagram of a Bessel light indicator structure;
FIG. 3 is an underwater Bessel optical visual guidance method of an embodiment of the present invention;
FIG. 4 is a diagram of an arrangement of underwater Bessel marker lights according to an embodiment of the present invention;
fig. 5 is a modal diagram of an underwater bessel marker light in the embodiment of the invention.
In the above figures, the reference numerals have the following meanings:
1. AUV; 2. an underwater camera; 3. a recovery device; 4. a marker light; 5. an imaging field of view; 6. a conventional marker light; 7. a line segment light beam; 8. a blue-green semiconductor laser; 9. a shaping lens; 10. bessel lenses.
Detailed Description
The invention discloses an underwater Bezier light vision guiding method for autonomous recovery of an underwater unmanned vehicle, which can solve the problems that the topological structure of an indicator light in a traditional underwater light vision guiding lamp is limited by mechanical size and the centroid of a light spot is difficult to accurately extract. In the autonomous AUV recovery process, an underwater camera arranged on the stem of the AUV can obtain an image of a marker light on a docking station recovery device, a marker light modal graph is output to an image processing module of the underwater camera, a light beam line segment is extracted through skeletonization processing of the marker light modal graph, the light beam line segment of a Bessel marker light is adopted as a characteristic line segment, the corresponding relation between the line segment in the marker light modal graph and the light beam line segment in a template can be obtained through characteristic matching, the conversion relation between a docking station coordinate system and a camera coordinate system is established by combining internal parameters of the underwater camera, and finally, the space coordinate and the attitude information of the AUV under the docking station coordinate system are given out by utilizing the conversion relation. The invention has good adaptability and strong flexibility, can realize the miniaturization of the mechanical structure of the marker light, realizes the accurate extraction of the characteristic line segment of the marker light beam and improves the positioning precision.
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
The Bessel lens is arranged at the outlet of a blue-green semiconductor laser 8 shown in figure 2, parallel light beams emitted by the blue-green semiconductor laser with a small divergence angle are integrated by a shaping lens 9, the parallel light beams are subjected to phase integration through the Bessel lens to form self-luminous positions, the light intensity distribution is kept unchanged within a certain distance, the high-intensity localized distribution is realized, and the light beam is in the form of a light beam line segment with a limited length. The length of the line segment light beam is determined by the base angle of the conical surface of the axicon and the radius of the light beam, so that the length of the line segment light beam can be adjusted by adjusting and adjusting the base angle of the conical surface of the Bessel lens.
Fig. 3 shows an underwater bessel light vision guiding method, an underwater camera 2 is assembled at the bow of an autonomous underwater unmanned vehicle AUV1, a docking station recovery device 3 has a funnel-shaped recovery station, two bessel marker lights with small divergence angles are installed at the left side and the right side of a recovery cover, the light beams of the two marker lights point oppositely (see fig. 4), the underwater camera obtains an underwater bessel marker light mode diagram (see fig. 5), two line segment light beams 7 form four characteristic points, namely two end points of each line segment light beam respectively correspond to one characteristic point, and a characteristic image formed by the line segment light beams is output to an image processing module.
In the invention, the Bezier lens at the outlet of the Bezier marker lamp is installed according to a target template of the marker lamp. The marker light target template is designed by a user according to the application requirement of the user by utilizing the characteristic point distance formed by the line segment light beam. The real length of the light beam section in the template is known, so that the coordinates of the characteristic points formed by two end points of the light beam section in the docking station coordinate system can be obtained. The underwater Bessel marker light modal diagram obtained by the underwater camera is mutually corresponding to the target template. Under the camera coordinate system, the coordinates of the feature points can be obtained. Because the coordinates of the feature points in the underwater Bessel marker light under the relative docking station coordinates are known, the coordinates and the attitude information of the camera coordinate system under the docking station coordinate system can be obtained by utilizing the corresponding relation between the coordinates of the feature points under the docking station coordinate system and the coordinates of the camera coordinate system. Because the camera is arranged at the bow of the AUV and the conversion relation between the coordinate system of the camera and the coordinate system of the AUV is known, the three-dimensional space coordinate and the attitude information of the AUV under the coordinate system of the docking station can be obtained, and the long-distance high-precision autonomous recovery of the AUV is finished.
The specific steps of this example are as follows:
the first step is as follows: selecting a Bessel lens according to a target template and installing the Bessel lens at the light-emitting position of a Bessel marker light, and further arranging the marker light on two sides of a recovery cover of a recovery device according to the target template, wherein the marker light template corresponds to an underwater Bessel marker light modal diagram obtained by a rear underwater camera as shown in figure 4;
the second step is that: when the AUV is recovered automatically, the marker lamp is turned on to form a line segment light beam in water;
the third step: an underwater camera at the head of the AUV obtains a Bessel marker light modal diagram;
the fourth step: an image processing module in the underwater camera performs image processing on the obtained underwater Bessel marker light modal graph to extract line segment light beams and obtain coordinates of the feature points under the camera coordinates;
the fifth step: an image processing module in the underwater camera obtains coordinates and posture information of a camera coordinate system under a docking station coordinate system by utilizing the corresponding relation between the coordinates of the underwater Bessel marker lamp under the docking station coordinate system and the coordinates of the camera coordinate system;
and a sixth step: an image processing module in the underwater camera provides three-dimensional space coordinates and posture information of the AUV under a docking station coordinate system by utilizing a known conversion relation between a camera coordinate system and the AUV coordinate system and outputs the three-dimensional space coordinates and the posture information to a control system of the AUV;
the seventh step: the AUV control system corrects navigation parameters according to the positioning information of the AUV control system under the docking station coordinate system, and aims at the bell-mouthed recovery cover of the recovery device;
eighth step: and repeating the third step to the seventh step until the AUV enters the recovery device and Bessel light vision guidance is finished.
The light beam line segment is formed by utilizing a Bessel lens, keeps light intensity distribution unchanged within a certain distance from a self-luminous position of a light beam, has high-intensity localized distribution, is formally represented as a light beam line segment with limited length, and the length of the light beam line segment can be changed by adjusting the Bessel lens.
The marker light target template is a specific target pattern formed by utilizing a line segment light beam according to the self requirement of a user, and the length of the line segment light beam in the template is known.
The method is characterized in that the coordinate and the attitude information of the camera coordinate system under the docking station coordinate system can be obtained by utilizing the corresponding relation between the coordinate of the marker light beam line segment under the docking station coordinate system and the coordinate of the camera coordinate system.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. An underwater Bessel light visual guidance method is characterized by comprising the following steps:
selecting a Bessel lens according to a target template of the marker lamp;
the Gaussian beam in the Bessel marker lamp is presented as a line segment beam after passing through the Bessel lens; the line-segment light beam is formed by utilizing a Bessel lens, keeps light intensity distribution unchanged within a certain distance from a self-luminous position, has high-intensity localized distribution, is in the form of a light beam line segment with limited length, and can be adjusted by the Bessel lens to change the length of the light beam line segment;
after the Bessel marker lamps are lightened, the light beam of each Bessel marker lamp forms a line segment, and the multiple light beam line segments form a marker lamp modal diagram;
in the autonomous recovery process of the underwater unmanned vehicle, an image processing module in an underwater camera performs image processing on an obtained underwater Bessel marker lamp modal graph to extract line segment light beams and obtain coordinates of feature points under camera coordinates;
an image processing module in the underwater camera obtains coordinates and posture information of a camera coordinate system under a docking station coordinate system by utilizing the corresponding relation between the coordinates of the underwater Bessel marker lamp under the docking station coordinate system and the coordinates of the camera coordinate system;
an image processing module in the underwater camera provides three-dimensional space coordinates and attitude information of the underwater unmanned vehicle under a docking station coordinate system by utilizing the known conversion relation between a camera coordinate system and the underwater unmanned vehicle coordinate system.
2. The underwater bezier light vision guide method of claim 1, wherein adjusting the bezier lens cone base angle enables length adjustment of the line segment light beam.
3. The underwater bezier light visual guidance method according to claim 1, wherein the marker light target template is a specific target pattern formed by using line segment light beams according to the user's own needs, and the length of the line segment light beam is known in the template.
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| CN103948353B (en) * | 2009-06-19 | 2016-07-06 | 三星电子株式会社 | Docking station for robot cleaner and the method to robot cleaner transmitting docking targeting signal |
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